Length Converter
Convert between length and distance units instantly: millimeters, centimeters, meters, kilometers, inches, feet, yards, miles, and nautical miles. Free, 100% in your browser.
Reference
How does length conversion work?
Length conversion uses fixed ratios between units. This tool converts through meters as the base unit — your input is first converted to meters, then from meters to every other unit. All conversion factors are exact or internationally standardized: 1 inch = 25.4 mm exactly (defined since 1959), 1 mile = 1,609.344 meters exactly, 1 nautical mile = 1,852 meters exactly.
Unit reference
Metric system: millimeter (mm), centimeter (cm), meter (m), kilometer (km) — based on powers of 10, used worldwide. Imperial/US: inch (in), foot (ft) = 12 inches, yard (yd) = 3 feet, mile (mi) = 5,280 feet — used primarily in the US, UK (partially), and Myanmar. Nautical mile (nmi) = 1,852 m — used in aviation and maritime navigation, defined as one minute of latitude along any meridian.
Common use cases
Travel — convert between kilometers and miles for road distances. Construction — switch between metric and imperial measurements for building plans. Science — convert lab measurements between millimeters, centimeters, and inches. Fitness — convert running distances (5K = 3.107 miles, marathon = 42.195 km). Sewing & crafts — convert pattern measurements between inches and centimeters. Navigation — convert nautical miles to kilometers for maritime or aviation distances.
Privacy
All calculations run 100% in your browser. No data is sent to any server.